Re-determination on the Sedimentary Age of Salawusu Formation
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摘要: 重新认识我国北方地区晚更新世河湖相标准地层——萨拉乌苏组的形成时代，对于萨拉乌苏组与马兰黄土的关系，与冰期气候对比等具有重要意义。笔者近年来根据野外层位对比和地层沉积相的划分，采用绝对年代控制，并结合黄土－古土壤序列研究的最新成果，初步建立了可以与黄土、深海沉积记录和冰期气候波动对比的萨拉乌苏组地层序列。认为河湖相沉积的萨拉乌苏组形成于约１４００００～７００００ａ.Ｂ.Ｐ.的末次间冰期，大致与深海氧同位素第５阶段对应，与黄土高原古土壤Ｓ１发育同期。城川组风成细砂形成于约７００００～１００００ａ.Ｂ.Ｐ的末次冰期，与黄土高原的马兰黄土是同期异相地质体.Abstract: The Salawusu River area is one of the standard sections of the Late Pleistocene strata in North Chi-na.However, there have been a lot of different views about the strata since the establishment of alawusu Formation, especially in the aspects of sedimentary facies, stratigraphic data and its climate sig-nificance.According to the stratigraphic subdivision, age dating and the analysis of the sedimentary fa-cies, the following recognitions can be gained: 1 The original Salawusu Formation could be further divided into Lishi Loess interbeded with sandysediments(Q22 ), Salawusuu Formation(Q,13 ), Cheng-chuan Formation(Q2,3 ), Dagouwan Formation (Q4 )and Dishaogouwan Formation(Q34 ).2 Salwusu Formation is mainly a fluvial-lacustrine deposit corresponding to the Stage 5 of deep seainδ18O and formed between about 140- 70 Ka.BP.Chengchuan Formation is mainly fossil aeolian sands,with some lacustrine silty-clay in the middle part, correspording to Stages 2- 4 of deep sea inδ18O andformed between 70- 10 Ka.BP.Dagouwan Formation is lacustrine sediments and black-paleosoil, indi-cating the warm-humid climate and formed in the middle-early period of Holocene.Dishaogouwan For-mation is mainly sub-loess and aeolian sands, representing the cold-dry climate and being believed to be-long to the late Holocene.3 As a fluvial-lacustrine sedimentary stratum, Salawusu Formation is quite different from its upperChengchuan Formation both in geochronology, lithology and sedimentary facies and in palaeontology.Chengchuan Formation and Malan Loess belong to heteropic deposits(sandy and loessic facies) formedcontemporaneously under the same wind action.4 As a flurial-lacustrine-aeolian-sand sequence by observing the Dishaogou profile in the SalawusuRiver area,its climatic records can compete with the records of loess and deep sea deposits, they may bedivided into 5 climatic periods just by oxygen isotope.It is suggested that the climatic change of this re-gion during the last interglacial period is synchronous withthat of the whole earth.
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Key words:
- Salawusu Formation /
- stratigraphic division /
- edimentary age
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